Skinning alive I consider the most gruesome way of killing someone... especially if the executioner is skilled... a great-great-great grandparent of mine, leader of a revolution against the Ottomans in Crete (Daskalogiannis) was killed that way. The executioner in his case was quite skilled and was skinning the man alive for more than 20 hours... just before the end, he was virtually left with no skin at all, from head to toes, but still was breathing, half-crazed by the tormenting pain and agony...

Impaling could also be extremely nasty... in some cases - when the executioner was a master in his "art" and could impale the victim from rectum to throat without harming any vital organs - the victims have survived up to 4 days, eventually submitting to internal bleeding!